Correction :

7 + 21 = 28	21 + 9 = 30
19 - 2 = 17	41 - 21 = 20
13 + 15 = 28	32 - 22 = 10
9 + 6 = 15	19 + 7 = 26
36 - 20 = 16	20 - 15 = 5
8 × 2 = 16	11 + 8 = 19
18 - 6 = 12	13 + 4 = 17
41 - 17 = 24	21 + 15 = 36
4 × 8 = 32	37 - 19 = 18
18 - 10 = 8	4 + 6 = 10